21,000 people evacuated as Indonesian volcano continues to spew ash for miles around

Aircraft have had to be diverted and more than 21,000 people evacuated after an Indonesian volcano erupted for the second day in a row.

Towering clouds of ash are being spewed out of Mount Sinabung in North Sumatra and thousands of villagers living on its slopes have been forced to head to emergency shelters, mosques and churches.

Homes and fields containing crops have been blanketed in heavy, gray soot and the air near the volcano is thick with the smell of sulphur.

Disruption: Flights have been diverted and thousands evacuated after Mount Sinabung erupted for the first time in 400 years

Evacuated: Nearby villages and crop fields have been covered in thick, gray ash

Ash: A resident attempts to escape from his village on a moped as the volcano erupts in the background

Mt Sinabung last erupted in 1600, so observers don't know its eruption pattern and admitted over the weekend that it had not been closely monitored before it erupted on Sunday.

Two people have died, one from breathing problems and the other from a heart attack, and two suffered injuries in road accidents as trucks, ambulances and buses were mobilised in the rescue operation.

Like other volcanoes along the Sumatra fault line - where the Eurasian and Pacific tectonic plates push against each other - it has the potential to be very destructive, according to disaster researcher Erick Ridzky.

A larger blast has the potential to obscure visibility he said, affecting air traffic in nearby Singapore and Malaysia.

Several domestic flights heading to the provincial capital of Medan have had to be diverted, according to the Indonesian Transportation Ministry.

Concerns: Farmers work in the village of Tanah Karo as the volcano erupts for the second day

Unknown: There are fears there could be a more powerful eruption, threatening thousands of Indonesian people

Sent home: School pupils wearing face masks listen to their headteacher before being sent home early

Surono, a government volcanologist, said: 'The problem is, we really have no idea what to expect.

'We don't know what set it off, how long it will continue or whether to expect pyroclastic flows or more powerful eruptions.'

So far, around 21,000 people have been evacuated and food, emergency tents and medicine is being flown to the area.

The government has set up public kitchens for refugees and handed out more than 17,000 respiratory masks.

Aid: The Indonesian government has set up public kitchens for refugees staying in mosques, churches and school buildings

Danger: Sumatra is within the Ring of Fire, an area prone to volcanoes and earthquakes

Indonesia is spread across 17,500 islands and is prone to volcanic eruptions and earthquakes because of its location within the so-called 'Ring of Fire' - a series of fault lines stretching from the Western Hemisphere through Japan and Southeast Asia.